Many regions of the world have inadequate rainfall to support lawns, gardens and other landscaping during dry periods. Sprinklers are commonly used to distribute water over such landscaping in commercial and residential environments. The water is supplied under pressure from municipal sources, wells and storage reservoirs.
So called “hose end” sprinklers were at one time in widespread use. As the name implies, they are devices connected to the end of a garden hose for ejecting water in a spray pattern over a lawn or garden. Fixed spray head sprinklers which are connected to an underground network of pipes have come into widespread use for watering smaller areas.
Impact drive sprinklers have been used to water landscaping over larger areas starting decades ago. They are mounted to the top of a fixed vertical pipe or riser and have a spring biased arm that oscillates about a vertical axis as a result of one end intercepting a stream of water ejected from a nozzle. The resultant torque causes the nozzle to gradually move over an adjustable arc and a reversing mechanism causes the nozzle to retrace the arc in a repetitive manner.
Rotor type sprinklers pioneered by Edwin J. Hunter of Hunter Industries, Inc. have largely supplanted impact drive sprinklers, particularly on golf courses and playing fields. Rotor type sprinklers are quieter, more reliable and distribute a more precise amount of precipitation more uniformly over a more accurately maintained sector size.
A rotor type sprinkler typically employs an extensible riser which pops up out of a fixed outer housing when water pressure is applied. The riser has a nozzle in a rotating head or turret mounted at the upper end of the riser. The riser incorporates a turbine which drives the rotating head via a gear train reduction, reversing mechanism and arc adjustment mechanism. One arc limit is typically fixed and the other arc limit is adjustable so that the turret and the nozzle it contains oscillate back and forth over a prescribed area to be watered. Some rotor type sprinklers have an automatic arc return mechanism so that if a vandal twists the turret outside of its arc limits, it will resume oscillation between the arc limits to prevent sidewalks, people and buildings from being watered. Rotor type sprinklers used on golf courses sometimes include an ON/OFF diaphragm valve in the base thereof which is pneumatically or electrically controlled.
Reversing mechanisms in rotor type sprinklers have generally been complex arrangements. See for example U.S. Pat. No. 4,625,914 of Sexton et al. which discloses the use of a swirl plate that is shifted to align different ports so that water jets will reverse a ball drive. More typical is the reversing mechanism disclosed in U.S. Pat. No. 3,107,056 of hunter in which a drive train includes a shifting mechanism that alternately shifts a pair of terminal gears carried on a shifting plate into and out of engagement with an internal gear at the ends of an oscillating stroke. U.S. Pat. No. 4,568,024 of Hunter discloses a more compact design for higher pop up stroke, higher volume rotor type sprinklers in which alternate driving pinion gears are shifted into driving engagement with an internal ring gear with the pressure angle of the engaging teeth being different for the different driving pinion gears to thereby balance the shifting force applied by a shifting mechanism. See also U.S. Pat. No. 4,718,605 of Hunter.
While the foregoing designs patented by Hunter have been commercially successful, they have space requirements that make them unsuitable for use in a pop-up sprinkler with a horizontal turbine and gear train reduction. Furthermore, they rely on the engagement of gear teeth with traditional tapers which do not perform a clutching function very well. If a maintenance worker, or a vandal, manually rotates the turret containing the nozzle relative to the lower outer housing of the sprinkler, the gear teeth do not slip over each other easily without resultant damage. Therefore elaborate clutching mechanisms are typically required to prevent damage to the reversing mechanism.